“Two are better than one”: a pilot study of how radiologist and oncologists can collaborate in target volume definition

The purpose of this study was to explore how radiologist and oncologists may work together efficiently and effectively to define target volume for radiotherapy treatment. Ten patients were chosen at random from those needing radiotherapy between December 2004 and June 2005. Sites of primary cancer included head and neck, pelvis, lung and brain. Diagnostic scans were available on the hospital PACS system and radiotherapy planning image data sets were available on the Eclipse radiotherapy planning system. A radiologist and two oncologists (one consultant, one senior registrar) outlined separately and without initial consultation the gross tumour volume (GTV). Analysis of target volume concordance rates was undertaken to assess and explore the reasons for any differences noted. Three of ten volumes defined (all head and neck tumours) were judged to be similar based on quantitative and qualitative data. There were varying degrees of difference in volume definition for the remaining seven patients. In three of these there were differences in GTV but when the treatment volume was drawn the differences were not clinically significant, as any areas of disagreement were included anyway in the fields in both plans. The remaining four cases had showed significant differences between the volume delineated by the oncologist and the radiologist. In all cases where the GTV was easily identifiable on the diagnostic and planning scans, there was concordance. In cases where the final treatment field used was much bigger than the GTV (e.g. a four-field box for pelvic fields) then small differences were negligible, although with conformal therapy these differences could become important. There were specific radiological anatomy learning points for the oncologists and the radiologist needed to be familiar with the process of treatment planning. A larger prospective study will continue to explore the potential gains from and the practicalities of collaborative working.